1. Field of the Invention
The present invention relates to a copying machine for copying a document through the steps of feeding out a plurality of stacked document sheets one by one, arranging two document sheets on a glass platen in series with respect to a document conveying direction, and copying images of the two document sheets onto one large-size sheet.
2. Description of the Prior Art
Conventionally, as a copying method using an electrophotographic method, from copy-saving and filing-space-saving points of view, a two-in-one mode copying method (hereinafter, referred to as "two-in-one mode") has been known by a Japanese Patent Laid-Open Publication No. 3-114071, a Japanese Patent Publication No. 5-73095, and the like. In this two-in-one mode, document sheets placed on a document tray of an automatic document feeder (ADF) are fed onto the glass platen one by one. On the glass platen, the document sheets are set in such a way that two sheets at each one time are arranged in series with respect to the document conveying direction and that one end of one document sheet is made coincident with an exposure reference (for example, one side line of a scale provided upstream or downstream of the glass platen in the document conveying direction) while one end of the other sheet is made coincident with the other end of the one document sheet. Then, the two document sheets are exposed to light by a single scanning operation. As a result, the two document sheets are copied onto a copying sheet of the same size as the original document sheet. More specifically, if the document sheets are of A4 size transverse, then the two document sheets are copied onto a sheet of A4 size longitudinal in reduction at a magnification factor of 0.707. After copying, the two document sheets on the glass platen are discharged to the discharge tray one after another. Then, another two document sheets (third and forth pages of the document) are set on the exposure position of the glass platen to be handled in the same manner as described above.
In the two-in-one mode as described above, however, when two document sheets exposed to light at the same time are continuously discharged, the rear end of the first page document sheet occasionally overlaps with the front end of the second page document, which causes the document sheets discharged to the discharge tray to be in reverse order.
Moreover, when prosecuting the two-in-one mode by the conventional copying machine, it is necessary to change the document set direction. More particularly, the document sheet should be set on the document tray in an upside-down condition.
And moreover, even if the copying machine is provided with a sorter having a stapler which staples the copied sheet, the sheet copied in two-in-one mode described above is not stapled on a proper portion, that is, on a left side shoulder of the sheet.